1. Field of the Invention
The present invention relates to a novel nutrient composition, more particularly a nutrient composition being a liquid or semisolid composition containing a specific amount of a protein, the composition having a particular volume-based median size and containing water-insoluble particles having a protein insolubilized by a divalent cation as the major component thereof.
2. Description of the Related Art
The six major nutrients essential for providing a healthy life style are carbohydrates, proteins, lipids, inorganic salts (minerals), vitamins, and dietary fibers. These nutrients are generally ingested through the regular diet. However, a nutrient composition collectively containing the nutrients is required by elderly persons who have difficulty masticating and swallowing due to cerebral vascular disorder, neuromuscular disorder, or the like, patients who have difficulty in oral intake due to consciousness disorder, postoperative patients, or the like. Although a concentrated liquid food is exemplified as such a nutrient composition, intake of such a liquid food may cause aspiration pneumonia in elderly persons with a reduced swallowing and mastication ability, in particular. Moreover, in the case of elderly persons with a reduced stomach size, the possible amount of food-intake thereof is extremely small. Accordingly, high-calorie nutrient compositions containing the necessary quantity of each nutrient, such as, proteins, minerals, and the like, are demanded by medical practice, and most available nutrient compositions are prepared to have a calorie density of 1 kcal/ml or more.
Most conventionally available fluid diets and nutritional supplements have a calorie density of 1 to 2 kcal/ml (a specific gravity of 1.07 to 1.14). Among them, there are nutrient compositions with a calorie density of 1 to 1.5 kcal/ml, the nutrient compositions independently enabling nutritional management (of bedridden elderly person, in particular). Such nutrient compositions are considered to be favorable formulation forms of enteral alimentation for achieving nutritional maintenance in persons administered them by tubal administration as well as oral intake.
However, in a conventionally available high-calorie nutrient composition of over 1.5 kcal/ml, the formulation amount of proteins or minerals is small with respect to the total energy of the nutrient composition, and therefore intake thereof only cannot maintain favorable nutrition conditions. In particular, an estimated average quantity of proteins necessary for persons aged over 70 is 40 to 50 g/day (Food intake standard in Japan, 2005). However, the formulation amount of the proteins is required to be preferably 6% or more, more preferably 7.5% or more, so that bedridden elderly persons intake the estimated average necessary quantity of proteins in almost 1,000 kcal/day, which is a practical energy intake amount.
Although a nutrient composition with high protein is known (Patent Document 1), the nutrient composition mainly aims to maintain favorable flavor with a high protein content, and the formulation amounts of other nutrients, particularly, minerals, such as sodiums, potassiums, calciums, magnesiums, or the like, are not considered to fully meet the above-mentioned food intake standard from the standpoint of emulsion stability.
In order to produce nutrient compositions which contain fats and oils and proteins and can be stored for a long time, emulsification is required to be performed using a high-pressure homogenizer, high-speed stirrer, or the like. However, in the case where a formulation liquid containing a large amount of such nutrients and minerals is prepared, the viscosity thereof is significantly increased, and thereby dissolution and formulation efficiencies of the raw materials decreases, and emulsification and sterilization treatments become difficult. Moreover, if the viscosity of the nutrient composition is increased, adhesive properties thereof are also increased, as a result of which the nutrient composition tends to adhere to and remain in the mouth or tube at the time of oral or tubal intake thereof, and therefore the nutrient composition does not easily enter the body.
In recent years, as an aspect of tubal intake, a method of tubal provision of nutrition through gastric fistula or enteroproctia has spread. The method of tubal provision of nutrition through gastric fistula or enteroproctia is a method in which a nutritional supplement is continuously or intermittently administered through a tube placed in an external fistula (fistulous opening) operatively or endoscopically formed in the esophagus, the stomach, or the jejunum (most of which is the stomach), to directly supply the nutritional supplement to the stomach or the intestine. Accordingly, such a method enables patients to ingest moisture and nutrition through the alimentary canal in the same way as that of healthy persons, and thereby the quality of life (hereinafter, abbreviated as QOL) of the patients is considered to be improved. Even in the case of the method of tubal provision of nutrition through gastric fistula or enteroproctia, if the viscosity of the nutrient composition is high and the adhesive properties thereof are strong at the time of administering the nutrient composition into the stomach or the intestine through a tube, the nutrient composition cannot be easily administered.
Thus, if the nutrient composition is administered to the patient, particularly through a tube, it is preferable that the viscosity-increase of the nutrient composition be suppressed and the adhesive properties inside the tube be reduced to make it possible for the nutrient composition to be administered by applying as small a pressure as possible. Although a method in which a protein hydrolysate, such as a peptide or amino acid, is formulated is conventionally proposed to suppress the viscosity-increase of the nutrient composition, and such a low-molecular weight protein material is generally known to promote emulsification degradation of fats, which results in the viscosity-decrease, problems such as emulsification destabilization or browning occurring caused by promotion of aminocarbonyl reaction arise.
Thus, it is quite difficult to prepare a nutrient composition with a high protein content easily-administerable for patients in various administration manners by uniformly dispersing, as an emulsion, the nutrient composition in water, a dispersion medium, without deteriorating the taste and flavor thereof.    Patent Document 1: Japanese Laid-Open Patent Application, No. 2004-97119.